Community Ecology Chapter 21

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2 I. Species InteractionsReview:A Population is a group of individuals of the same speciesA Community is a group of interacting populations of many species

3 5 ways species interact:PredationCompetitionParasitismMutualismCommensalism(Symbiotic relationships -next 3)Categories are based on whether each species causesbenefit or harm to the other in the relationship

10 Mimicry Defense mechanism for preyPredator- Prey AdaptationsMimicryDefense mechanism for preyDeception - A harmless species LOOKS like a harmful, poisonous or bad tasting species.A predator will avoid BOTH species

11 Monarch and viceroy butterflies are an example of mimicrySimilar in appearance & are distasteful to predators.A strong black line traversing the middle of the hindwing distinguishes the monarch (right) from the viceroy (left).

13 2. Competition*The relationship between species in which they attempt to use the same limited resource.*To fit into a niche, an organism must compete.*Competition occurs when fundamental niches overlap

14 Competitive Exclusion- When 2 species of paramecium are grown in same media- note that 1 species wins, other eliminated.

15 Character Displacement & Resource PartitioningCompetition Interactions:Character Displacement & Resource PartitioningEvolution of niche differences or anatomical differences to lessen competitionOccurs becauseCompetition may eliminate species from the community.Species may change under the pressure of natural selectionExample- Darwin’s finches have different shaped beaks & eat different foods

16 Competition Interactions:Organisms can compete even if they never come into contact with each other.Examples:**One species can feed on a certain plant at night while another eats the same plant in the daytime.**2 Flowers compete for pollinators

17 What happens when competition for the same niche is unnaturally changed?Example- the Red Fire Ant- originally from South America-competes for the same niche as the native Black AntWhy is the Fire ant dominating?

18 Red Imported Fire AntIntroduced from western Brazil- quickly becomes the number 1 ant pest wherever it occurs. The main reason -its natural enemies from its native habitat were left behind in South AmericaQueen ants can live 7 years or more, while worker ants generally live about 5 weeks, although they can survive much longer.The venom burns like a hot match and causes tiny blisters or white pustules that persist for days if left untreated or for weeks if scratched or infected and may leave permanent scars.

20 3. Parasitism Host- organism that provides nourishmentOrganism that lives on or in another organism and feeds on it without immediately killing it.Parasites HURT the hostHost- organism that provides nourishmentParasite- Organism that does the feedingMost populations are negatively affected- weakened, sickened, shorten lifespanParasitic micro-organisms(roundworm, protozoan, bacterium,fungus, yeast)

21 Niche:role that a species plays in its environment.Fundamental Niche: range of conditions that an organism can potentially tolerate.Realized Niche: The niche that the species actually uses.

24 5. CommensalismA relationship in which 1 species benefits and the other is neither helped or harmedExample:Remoras are fish that attachthemselves to sharks. Theremoras get food but the sharksdo not appear to get anything back. remoras on tiger shark

25 II. Properties of CommunitiesSpecies Richness- number of species it contains.(greater number of organisms= increased species richness)Species diversity- how common each species is in the community (takes into account the population size - are some species rare or are their lots of most populations?)

26 Patterns of Species RichnessSpecies- Area Effect- larger areas contain more species than smaller areas.Predators may promote richness by preventing competitive exclusion in their prey.Community Stability- resistance to change & disturbances.

27 III. SuccessionA regular pattern of change over time in the types of species in a community.Begins when an area is made partially or completely devoid of vegetation because of a disturbance.2 types- primary & secondary

34 Secondary SuccessionIs the sequential replacement of species after a disruption of an existing ecosystem.FiresHurricanesBurned, flattened forest after volcanic eruptionAbandoned farmlandNew pond formed

36 Regrowth, four years after major forest fire, Colorado. In May, 1996ecolibrary.org/page/DP420

37 Primary succession is slower than secondary succession because it begins where there is no soil.It takes several hundred years to produce fertile soil naturally.Secondary succession can occur in less than a hundred years

41 Same ground 2 years later, now covered in grass, low flowering plants

42 Example of a Pioneer SpeciesLichens- a mutualistic association between fungi & a photosynthetic organism- either a cyanobacteria or an algae.Lichens , along with weathering, break up barren rock in primary succession.Decaying dead lichens accumulates and is the first step in creating soil.

46 Climax CommunityPlant community that no longer undergoes changes in species composition due to succession.Considered the “stable end point”.Doesn’t “really “ exist- because communities continue to change-Regularly “reset” due to disturbances.